Apple, Google, and Facebook also make use of this technique, according to Bloomberg.

This has been used to help law enforcement in cases of sexual assault and other crimes.

A spokesperson with Amazon released the following statement:

"We take the security and privacy of our customers' personal information seriously. We only annotate an extremely small number of interactions from a random set of customers in order to improve the customer experience. For example, this information helps us train our speech recognition and natural language understanding systems, so Alexa can better understand your requests, and ensure the service works well for everyone. We have strict technical and operational safeguards, and have a zero tolerance policy for the abuse of our system. Employees do not have direct access to information that can identify the person or account as part of this workflow. While all information is treated with high confidentiality and we use multi-factor authentication to restrict access, service encryption, and audits of our control environment to protect it, customers can delete their voice recordings associated with their account at any time."